Notify hotwording extension of microphone state change.

chrome/common/extensions/api/hotword_private.idl

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // The <code>chrome.hotwordPrivate</code> API allows extensions to access and
 // mutate the preference for enabling hotword search. It also provides
 // information on whether the hotword search is available. This API provides an
 // event interface to transmit to the extension a signal that the preference fo
 // hotword search has change.
 //
@@ skipping 164 matching lines @@
 
     // Fired when a hotword has triggered.
     static void onHotwordTriggered();
 
     // Fired when the speaker model should be deleted.
     static void onDeleteSpeakerModel();
 
     // Fired when the browser wants to find out whether the speaker model
     // exists.
     static void onSpeakerModelExists();
+
+    // Fired when the microphone state changes.
+    static void onMicrophoneStateChanged(boolean enabled);
   };
 };